The costs of obesity are high and rising and affect all ages, yet there is little information about the cost-effectiveness of obesity treatments and interventions among children. Although much work is being done in this area, much of it is piecemeal, with the studies involved will not following a common methodology, making comparisons of cost-effectiveness across studies very difficult. What is needed is a comprehensive approach to understanding obesity as a public health problem and an issue of societal resource allocation. This application presents such a framework and the project will refine, validate, and verify a hybrid discrete- event and agent-based simulation model. Methods: We develop, validate, and utilize a hybrid model combining discrete-event simulation (DES) and agent-based modeling (ABM) to examine obesity in children from a system perspective. DES is the best choice in situations where the model will be used for multiple resource questions, agents are autonomous, and resources are potentially constrained. Our model has four sub-models. (1)The epidemiological risk model will model obesity status over time, reflecting transition probabilities as well as contextual factors, such as the built environment and school characteristics. (2) We use the disease model to model health care costs for screening and treatment of hyperlipidemia, primarily, and other obesity-related conditions. For each period, each individual will accrue the expected value of costs from other health conditions related to obesity. (3) The medical system model examines the effects of personal and community characteristics on the likelihood of seeing a physician and receiving different types of screening or treatment. Finally, the child adult model uses the outputs from our simulation and similar models that have been developed for adults to examine the effects of childhood obesity into adulthood. We will use the model to examine three important policy-relevant questions: (a) What is the economic impact of health care reform (CHIPRA and PPACA) on childhood obesity and its costs to children, their families, taxpayers, and society? (b) What is a cost-effective method for screening and treatment for hyperlipidemia among children? (c)What is the cost-effectiveness of a school- based universal obesity prevention programs?